Piezoelectric/electrostrictive ceramics sintered body

ABSTRACT

A piezoelectric/electrostrictive ceramic sintered body has a microstructure in which a matrix phase and an additional material phase having different compositions coexist and the additional material phase is dispersed in the matrix phase. A residual strain ratio of the additional material phase alone is larger than a residual strain ratio of the matrix phase alone. The matrix phase and the additional material phase have a composition in which a Mn compound containing Mn atoms of 0 parts by mole or more and 3 parts by mole or less and a Ba compound containing Ba atoms of 0 parts by mole or more and 1 part by mole or less are contained in a composite of 100 parts by mole represented by a general formula {Li y (Na 1-x K x ) 1-y } a (Nb 1-z-w Ta z Sb w )O 3 , where a, x, y, z and w satisfy 0.9≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.2, 0≦z≦0.5 and 0≦w≦0.1, respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric/electrostrictiveceramic sintered body.

2. Description of Related Art

A piezoelectric/electrostrictive actuator has an advantage thatdisplacement can be controlled in a submicron order with accuracy. Inparticular, a piezoelectric/electrostrictive actuator, in which apiezoelectric/electrostrictive ceramic sintered body is used as apiezoelectric/electrostrictive body, has advantages such as highelectromechanical conversion efficiency, large generating force, highresponse speed, high durability and less power consumption, in additionto the advantage that displacement can be controlled with accuracy.Thanks to these advantages, the piezoelectric/electrostrictive actuatoris used in a head of an inkjet printer, an injector of a diesel engineand the like.

Lead-zirconate-titanate-based piezoelectric/electrostrictive ceramic hasbeen conventionally used as piezoelectric/electrostrictive ceramic for apiezoelectric/electrostrictive actuator. However, there are growingfears that elution of lead from a sintered body may affect globalenvironment, which also leads to a study of alkaline-niobate-basedpiezoelectric/electrostrictive ceramic.

Patent Literature 1 is a prior art document that describes the inventionknown to the public through publication related to the presentinvention. Patent Literature 1 relates to the alkaline-niobate-basedpiezoelectric/electrostrictive ceramic having a microstructure in whicha core particle is enclosed by shell particles.

PRIOR ART LITERATURE Patent Literature

-   {Patent Literature 1} Japanese Patent Application Laid-Open No.    2007-204336

However, in the conventional alkaline-niobate-basedpiezoelectric/electrostrictive ceramic, electric field induced strainduring application of high electric field, which is important for apiezoelectric/electrostrictive actuator, is not necessarily sufficient.

The piezoelectric/electrostrictive ceramic of Patent Literature 1 isprovided for improving an insulating property, in which electric fieldinduced strain during application of high electric field is notnecessarily sufficient.

The present invention has been made to solve the above-mentionedproblem, and an object thereof is to provide an alkaline-niobate-basedpiezoelectric/electrostrictive ceramic sintered body that has anincreased electric field induced strain during application of highelectric field.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problem, the following means areprovided.

A first invention relates to a piezoelectric/electrostrictive ceramicsintered body, which has a microstructure in which a matrix phase and anadditional material phase having different compositions coexist and theadditional material phase is dispersed in the matrix phase, wherein: aresidual strain ratio of the additional material phase alone is largerthan a residual strain ratio of the matrix phase alone; a composition ofthe matrix phase and a composition of the additional material phase areselected from a composition range of a composite in which at least oneof a Mn compound containing Mn atoms of 0 parts by mole or more and 3parts by mole or less and a Ba compound containing Ba atoms of 0 partsby mole or more and 1 part by mole or less are contained in a compoundof 100 parts by mole represented by a general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃, where a, x,y, z and w satisfy 0.9≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.2, 0≦z≦0.5 and 0≦w≦0.1,respectively; and zero or one kind of element is not common toconstituent elements of the matrix phase and constituent elements of theadditional material phase in comparison therebetween.

According to a second invention, in the piezoelectric/electrostrictiveceramic sintered body of the first invention, the composition of theadditional material phase is selected so that the residual strain ratioin a long side direction of a rectangular plate polarized in a thicknessdirection of the additional material phase alone is 800 ppm or more.

According to a third invention, in the first or second invention, thepiezoelectric/electrostrictive ceramic sintered body contains theadditional material phase of 1% by volume or more and 45% by volume orless.

According to a fourth invention, in the piezoelectric/electrostrictiveceramic sintered body of any one of the first to third inventions, z ofthe additional material phase is smaller than z of the matrix phase.

According to a fifth invention, in the piezoelectric/electrostrictiveceramic sintered body of any one of the first to fourth inventions, y ofthe additional material phase is smaller than y of the matrix phase.

According to a sixth invention, in the piezoelectric/electrostrictiveceramic sintered body of any one of the first to fifth inventions, a ofthe additional material phase is larger than a of the matrix phase.

According to a seventh invention, in the piezoelectric/electrostrictiveceramic sintered body of any one of the first to sixth inventions, w ofthe additional material phase is smaller than w of the matrix phase.

According to an eighth invention, in the piezoelectric/electrostrictiveceramic sintered body of any one of the first to seventh inventions, xof the additional material phase is larger than x of the matrix phase.

According to the present invention, there is provided analkaline-niobate-based piezoelectric/electrostrictive ceramic sinteredbody that has an increased electric field induced strain duringapplication of high electric field.

Objects, features, aspects and advantages of the present invention willbecome more apparent from the following detailed description and theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 This is a cross-sectional view of apiezoelectric/electrostrictive actuator;

FIG. 2 This is another cross-sectional view of apiezoelectric/electrostrictive actuator;

FIG. 3 This is still another cross-sectional view of apiezoelectric/electrostrictive actuator;

FIG. 4 This is a perspective view of a piezoelectric/electrostrictiveactuator;

FIG. 5 This is a vertical cross-sectional view of thepiezoelectric/electrostrictive actuator;

FIG. 6 This is a lateral cross-sectional view of thepiezoelectric/electrostrictive actuator; and

FIG. 7 This is an exploded perspective view of part of thepiezoelectric/electrostrictive actuator.

DETAILED DESCRIPTION OF EMBODIMENTS THE INVENTION 1 First Embodiment

A first embodiment relates to a piezoelectric/electrostrictive ceramicsintered body.

(Ceramic Composite)

The piezoelectric/electrostrictive ceramic sintered body according tothe first embodiment is a ceramic composite (ceramic complex body)having a microstructure in which a matrix phase and an additionalmaterial phase that have different compositions coexist and theadditional material phase is dispersed in the matrix phase. Whether thepiezoelectric/electrostrictive ceramic sintered body is a ceramiccomposite is confirmed by analyzing the element distribution of a mirrorpolished surface of a piezoelectric/electrostrictive ceramic sinteredbody by, for example, electron probe micro analysis (EPMA). If amechanically polished surface of a piezoelectric/electrostrictiveceramic sintered body is subjected to elemental analysis by FE (fieldemission)-EPMA (for example, with “JXA-8530F” of JEOL Ltd. (Akishima,Tokyo)) to obtain an elemental concentration map of the mechanicallypolished surface, in a case where the piezoelectric/electrostrictiveceramic sintered body is a ceramic composite, a difference incomposition between a matrix phase and an additional material phase isobserved, whereby the matrix phase and the additional material phase aredistinguished from each other.

(Residual Strain Ratio)

A residual strain ratio of an additional material phase alone is largerthan a residual strain ratio of a matrix phase alone. For this reason,when poling is performed on a piezoelectric/electrostrictive ceramicsintered body (ceramic complex body), the additional material phase isdistorted more than the matrix phase. As a result, inside the matrixphase, a compressive stress is generated in a direction parallel to apolarization field, whereas a tensile stress is generated in a directionperpendicular to the polarization field. The compressive stress andtensile stress increase the reversibility in a non-180° domain of thematrix phase. As the reversibility in the non-180° domain of the matrixphase increases, a residual strain ratio of the matrix phase alonedecreases and a reversible strain ratio increases, with the result thatan electric field induced strain during application of high electricfield increases in the piezoelectric/electrostrictive ceramic sinteredbody.

The “residual strain ratio” represents a ratio ΔL/L of a dimensionalchange ΔL of a piezoelectric/electrostrictive ceramic sintered bodybefore/after poling to a dimension L of thepiezoelectric/electrostrictive ceramic sintered body before poling.Further, a specific value of residual strain ratio described belowrepresents a residual strain ratio in a long side direction of arectangular plate polarized in a thickness direction.

A total strain ratio obtained when a piezoelectric/electrostrictiveceramic sintered body that has yet to be polarized is subjected topoling is a sum of a residual strain ratio remaining after thepolarization field is removed and a reversible strain ratio whichreversibly increases/decreases correspondingly to a driving electricfield. Accordingly, a reversible strain ratio (that is, electric fieldinduced strain) increases as a residual strain ratio decreases.

The residual strain ratios of an additional material phase “alone” and amatrix phase “alone” are specified by respectively manufacturingpiezoelectric/electrostrictive ceramic sintered bodies that have thesame compositions as those of an additional material phase and a matrixphase and measuring residual strain ratios thereof. The magnitude ofresidual strain ratio is judged by a residual strain ratio in a casewhere poling is performed under the same poling conditions.

The residual strain ratio of an additional material phase alone isdesirably 800 ppm or more. This is because the effect of increasing anelectric field induced strain during application of high electric fieldis obtained more easily if a residual strain ratio of an additionalmaterial phase alone is equal to or larger than the above-mentionedlower limit.

A difference between a residual strain ratio of a matrix phase alone anda residual strain ratio of an additional material phase alone isdesirably 50 ppm or more. This is because, if a difference between aresidual strain ratio of a matrix phase alone and a residual strainratio of an additional material phase alone is less than theabove-mentioned lower limit, the effect of increasing an electric fieldinduced strain during application of high electric field is hard to beobtained even when no type of element that is not common to a matrixphase and an additional material phase is found as a result of acomparison between constituent elements thereof.

(Content of Additional Material Phase)

An additional material phase contained in apiezoelectric/electrostrictive ceramic sintered body is desirably 1% byvolume or more and 45% by volume or less, more desirably 2% by volume ormore and 35% by volume or less, and particularly desirably 4% by volumeor more and 25% by volume or less. This is because a content of anadditional material phase smaller than the lower limits of theabove-mentioned ranges decreases the reversibility in the non-180°domain of the matrix phase, which makes it difficult to obtain theeffect of increasing an electric field induced strain during applicationof high electric field. On the other hand, if a content of an additionalmaterial phase is larger than the upper limits of the above-mentionedranges, a contribution of an additional material phase, which has asmall reversible strain ratio due to a large residual strain ratio, toan electric field induced strain during application of high electricfield increases, or densification of a ceramic complex body tends to bedifficult.

(Compositions of Matrix Phase and Additional Material Phase)

The compositions of a matrix phase and an additional material phase areselected from the same composition range. The matrix phase and theadditional material phase have the composition in which at least one ofa Mn compound containing Mn atoms of 0 parts by mole or more and 3 partsby mole or less and a Ba compound containing Ba atoms of 0 parts by moleor more and 1 parts by mole or less are contained in a compound of 100parts by mole represented by a general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃, where a, x,y, z and w satisfy 0.9≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.2, 0≦z≦0.5 and 0≦w≦0.1,respectively.

More desirably, the matrix phase and the additional material phase havethe composition in which at least one of a Mn compound containing Mnatoms of 0 parts by mole or more and 1 part by mole or less and a Bacompound containing Ba atoms of 0 parts by mole or more and 0.5 parts bymole or less are contained in a compound of 100 parts by molerepresented by a general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃, where a, x,y, z and w satisfy 1≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.1, 0≦z≦0.3 and 0≦w≦0.05,respectively.

Particularly desirably, the matrix phase and the additional materialphase have the composition in which at least one of a Mn compoundcontaining Mn atoms of 0 parts by mole or more and 1 part by mole orless and a Ba compound containing Ba atoms of 0 parts by mole or moreand 0.5 parts by mole or less are contained in a compound of 100 partsby mole represented by a general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃, where a, x,y, z and w satisfy 1<a≦1.1, 0.3≦x≦0.7, 0.02≦y≦0.1, 0≦z≦0.3 and 0≦w≦0.05,respectively.

An A/B ratio α of a molar amount of A-site elements Li, Na and K to amolar amount of B-site elements Nb, Ta and Sb is set in a particularlydesirable composition such that 1<a for promoting grain growth anddensification of a sintered body. Further, when the A/B ratio is setsuch that a≦1.1, dielectric loss decreases and an electric field inducedstrain during application of high electric field increases.

The reason why the compositions of a matrix phase and an additionalmaterial phase are selected in those composition ranges is that anelectric field induced strain during application of high electric fieldtends to become insufficient in a case where the matrix phase and theadditional material phase have compositions outside those compositionranges.

A Mn compound is added for facilitating poling and increasing anelectric field induced strain during application of high electric fieldowing to synergistic effect with substitution of Sb. It suffices thatthe content of a Mn compound is extremely small. For example, even in acase where only a Mn compound of 0.001 parts by mole is contained in thecomposition of 100 parts by mole represented by the general formulaabove in terms of Mn atom, the effect obtained by adding a Mn compoundis exhibited.

A Ba compound is added for increasing an electric field induced strainduring application of high electric field. In a case where a Ba compoundis added, it is desirably contained such that a content thereof to aperovskite-type oxide of 100 parts by mole in terms of Ba atom is 0.01parts by mole or more and 0.5 parts by mole or less. This is because theeffect of improving an electric field induced strain during applicationof high electric field is hard to be obtained if the content of Bacompound falls below this range. On the other hand, if the content of Bacompound exceeds this range, a secondary phase tends to separate, whichreduces an electric field induced strain during application of highelectric field. Although it is preferable that a Ba compound becontained in both of a matrix phase and an additional material phase, itmay be contained in one of the matrix phase and the additional materialphase.

In order to make the residual strain ratio of an additional materialphase alone larger than the residual strain ratio of a matrix phasealone, the composition of the matrix phase is different from thecomposition of the additional material phase. In order to make theresidual strain ratio of an additional material phase alone larger thanthe residual strain ratio of a matrix phase alone, it is desirable tomake z of the general formula above that indicates a Ta amount smallerin an additional material phase compared with a matrix phase, make y ofthe general formula above that indicates a Li amount smaller in anadditional material phase compared with a matrix phase, and make the A/Bratio a larger in an additional material phase compared with a matrixphase. This relationship between the composition of a matrix phase andthe composition of an additional material phase is opposite to that ofPatent Literature 1.

Further, w of the general formula above that indicates a Sb amount isdesirably made smaller in an additional material phase compared with amatrix phase, and x of the general formula above that indicates a Kamount is desirably made larger in an additional material phase comparedwith a matrix phase.

Desirably, there is no element that is not common to the constituentelements of a matrix phase and the constituent elements of an additionalmaterial phase when they are compared with each other. Accordingly,inter-diffusion between the matrix phase and the additional materialphase is suppressed during firing, and an electric field induced strainduring application of high electric field in thepiezoelectric/electrostrictive ceramic increases due to complication ofthe matrix phase and the additional material phase. Note that in thecase where there is a large difference between the residual strain ratioof a matrix phase alone and the residual strain ratio of an additionalmaterial phase alone as described above, a similar effect is obtainedeven if there is one type of element that is not common to both.

A matrix phase is a solid solution having the above-mentionedcomposition, which may contain a slight amount of grain boundarysegregation. Similarly, an additional material phase is a solid solutionhaving the above-mentioned composition, which may contain a slightamount of grain boundary segregation. A Mn compound and a Ba compoundturn into oxides in the calcination step or the firing step, and faun asolid solution with a perovskite-type oxide represented by the generalformula above. Note that in any of the matrix phase and the additionalmaterial phase, part of Mn, Ba or Sb may be segregated in a grainboundary as an oxide or other compound.

(Crystal Structure)

In the matrix phase and the additional material phase that have theabove-mentioned compositions, a crystal system changes in the order oforthorhombic phase, tetragonal phase and cubic phase along with atemperature rise. The composition of the matrix phase is desirablyselected such that a crystal system at a temperature of use has atetragonal phase. The composition of the additional material phase isdesirably selected such that a crystal system at a temperature of usehas a tetragonal phase or an orthorhombic phase.

(Orientation)

The orientation of a (001)plane on a surface perpendicular to apolarization field of a ceramic complex body is desirably small. Thissuggests increased reversibility of non-180° domain.

The orientation of a (001)plane on a surface perpendicular to apolarization field is checked by, for example, projecting a ratioI002/I200 of a diffraction peak strength I002 of a (002)plane to adiffraction peak strength I200 of a (200)plane in an X-ray diffractionprofile on the surface perpendicular to a polarization field.

(Coercive Electric Field)

The coercive electric field of the additional material phase isdesirably large. This is because a large coercive electric fielddecreases the reversibility in a non-90° domain, and thus a residualstrain ratio tends to increase.

(Production of Material Powders of Matrix Phase)

In producing material powders of the matrix phase, raw materialscontaining constituent elements (Li, Na, K, Nb, Ta, Sb, Mn, Ba and thelike) of a matrix phase are weighed so as to satisfy a predeterminedmolar ratio, and then mixed. A solvent may be added as a dispersingmedium during mixing. Non-limiting examples of mixing methods includemixing in a mortar, ball mill, pot mill, bead mill, hammer mill and jetmill. As a raw material, an oxide or a compound of carbonate, tartrateor the like that becomes an oxide in the calcination step is used. As adispersing medium, an organic solvent such as ethanol, toluene andacetone is used.

Mixed material powders are obtained as such by mixing in a case where asolvent is not added during mixing, whereas in a case where a solvent isadded during mixing, the obtained mixed slurry is dried by using a drieror the like or by an operation such as filtering, to thereby obtainmixed material powders. Calcination is performed on the obtained mixedmaterial powders at 600 to 1,300° C., whereby the powders of materialpowders of the matrix phase are synthesized. Calcination may beperformed only once or two or more times. In the case of performingcalcination two or more times, the conditions of each calcination may bethe same or different from each other. The atmosphere of calcination maybe air atmosphere or an oxygen atmosphere. The synthesized materialpowders of matrix phase may be, for example, ground or classified, tothereby adjust a particle diameter of material powders of matrix phase.A temperature increase rate and a temperature decrease rate duringcalcination are desirably 20 to 2,000° C./hour and the time for holdingcalcination temperature is desirably 30 seconds to 20 hours.

Powders of mixed materials are subjected to calcination along agenerally used one-step calcination schedule (trapezoidal temperatureprofile). For example, powders of mixed materials are calcinated along aone-step calcination schedule including (I) a first step of increasing atemperature from a room temperature to a first calcination temperatureof 600 to 1,300° C. at a temperature increase rate of 20 to 2,000°C./hour and holding the first calcination temperature, and after that,the temperature is immediately decreased to a room temperature at atemperature decrease rate of 20 to 2,000° C./hour.

The powders of mixed materials may be calcinated along a multi-stepcalcination schedule. For example, powders of mixed materials may becalcinated along a two-step calcination schedule including: (1) a firststep of increasing a temperature from a room temperature to a firstcalcination temperature of 600 to 800° C. and holding the firstcalcination temperature; and (2) a second step of increasing thetemperature from the first calcination temperature to a secondcalcination temperature of 800 to 1,300° C. and holding the secondcalcination temperature, and after that, the temperature is decreased toa room temperature.

Alternatively, powders of mixed materials are calcinated along atwo-step calcination schedule including: (1) a first step of increasinga temperature from a room temperature to a first calcination temperatureof 900 to 1,300° C. at a temperature increase rate of 500° C./hour orhigher and holding the first calcination temperature; and (2) a secondstep of decreasing the temperature from the first calcinationtemperature to a second calcination temperature of 600 to 900° C. at atemperature decrease rate of 200° C./hour or higher and holding thesecond calcination temperature, and after that, the temperature isdecreased to a room temperature.

Powders of mixed materials may be calcinated along a three-stepcalcination schedule in which the above-mentioned two patterns oftwo-step calcination schedules are combined.

In a case where grinding is performed, for example, there is used agrinding method such as a mortar grinding, a pot mill, a bead mill, ahammer mill, a jet mill and the method of pressing the materials againsta mesh or a screen.

A median particle diameter of material powders of matrix phase isdesirably 0.1 to 1 μm.

The material powders of matrix phase may be synthesized by synthesizingan intermediate represented by the general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃ and thencausing the raw materials of Mn and Ba to react with the intermediate.Material powders of matrix phase or an intermediate thereof may besynthesized by the alkoxide method or coprecipatation method not by thesolid-phase reaction method. Alternatively, a solid solution of B-siteelements (for example, complex oxide of a plurality of B-site elements)may be synthesized and then mixed with raw materials containing A-siteelements for calcination, thereby synthesizing powders of aperovskite-type oxide.

(Production of Material Powders of Additional Material Phase)

In producing material powders of additional material phase, separatelyfrom the production of material powders of matrix phase, intermediatematerial powders of additional material phase are synthesized in asimilar procedure to that of the production of material powders ofmatrix phase.

The intermediate material powders of additional material phase are onceformed, and then subjected to firing at 600 to 1,300° C. (desirably, at900 to 1,100° C.). Firing may be performed as powders without formingthe intermediate material powders of additional material phase. Theatmosphere during firing may be an air atmosphere or an oxygenatmosphere. A temperature increase rate and a temperature decrease rateduring firing are desirably 20 to 2,000° C./hour, and the time formaintaining the firing temperature is desirably 30 seconds to 10 hours.

The intermediate material powders of additional material phase aresubjected to firing along a generally used one-step firing schedule. Forexample, the intermediate material powders of additional material phaseare subjected to firing along a one-step firing schedule including (1) afirst step of increasing a temperature from a room temperature to afirst firing temperature of 900 to 1,300° C. at a temperature increaserate of 20 to 2,000° C./hour and holding the first firing temperature,and after that, the temperature is immediately decreased to a roomtemperature at a temperature decrease rate of 20 to 2,000° C./hour.

The intermediate material powders of additional material phase may besubjected to firing along a multi-step firing schedule. For example, theintermediate material powders are subjected to firing along a two-stepfiring schedule including: (1) a first step of increasing a temperaturefrom a room temperature to a first firing temperature of 600 to 950° C.and holding the first firing temperature; and (2) a second step ofincreasing the temperature from the first firing temperature to a secondfiring temperature of 950 to 1,300° C. and holding the second firingtemperature, and after that, the temperature is decreased to a roomtemperature.

Alternatively, the intermediate material powders are subjected to firingalong a two-step firing schedule including: (1) a first step ofincreasing a temperature from a room temperature to a first firingtemperature of 1,000 to 1,300° C. at a temperature increase rate of 500°C./hour or higher and holding the first firing temperature; and (2) asecond step of decreasing the temperature from the first firingtemperature to a second firing temperature of 600 to 1,000° C. at atemperature decrease rate of 200° C./hour or higher and holding thesecond firing temperature, and after that, the temperature is decreasedto a room temperature.

The intermediate material powders of additional material phase may besubjected to firing along a three-step firing schedule in which theabove-mentioned two patterns of two-step firing schedules are combined.

A piezoelectric/electrostrictive ceramic sintered body formed of theobtained additional material phase alone is ground and classified, andthen turns into material powders of additional material phase.Non-limiting examples of grinding methods include a mortar grinding, apot mill, a bead mill, a hammer mill, a jet mill and the method ofpressing the sintered body against a mesh or a screen. Non-limitingexamples of classifying methods include a method of sifting with a mesh,a method using elutriation, a method using a classifier such as an airsifter, a sieve classifier and an elbow-jet classifier.

A median particle diameter of material powders of additional materialphase is desirably 0.5 to 20 μm, more desirably 0.5 to 10 μm, andparticularly desirably 0.5 to 5 μm. This is because inter-diffusion of amatrix phase and an additional material phase is suppressed if theparticle diameter of material powders of additional material phase isequal to or more than lower limits of those ranges. On the other hand,if the median particle diameter of material powders of additionalmaterial phase is equal to or less than upper limits of those ranges, aceramic complex body is easily densified, with the result that stablestrain characteristics are obtained.

The material powders of additional material phase obtained by grindingand classifying a piezoelectric/electrostrictive ceramic sintered bodyhave lower reactivity compared with material powders of matrix phase.Accordingly, even when firing is performed in the environment in whichmaterial powders of matrix phase and material powders of additionalmaterial phase coexist, there hardly occurs reaction between materialpowders of matrix phase and material powders of additional materialphase. This contributes to the suppression of inter-diffusion of amatrix phase and an additional material phase.

(Production of Piezoelectric/Electrostrictive Ceramic Sintered Body)

In producing a piezoelectric/electrostrictive ceramic sintered body,material powders of matrix phase and material powders of additionalmaterial phase are mixed together. A dispersing medium may be addedduring mixing. As a dispersing medium, organic solvents such as ethanol,toluene and acetone are used. While the mixing method is notparticularly limited, a mortar mixing, pot mill, bead mill, hammer milland jet mill are used. Mixed materials are obtained as such throughmixing in a case where a dispersing medium is not added, whereas in acase where a dispersing medium is added, the mixed slurry obtainedbefore for forming is dried, to thereby obtain mixed materials.

The obtained mixed materials (hereinafter, referred to as “compositematerial powders”) are formed and subjected to firing. The firingtemperature is desirably 600 to 1,300° C. The atmosphere of firing isdesirably an oxygen atmosphere, and may be an air atmosphere. Firing maybe performed in the state in which powders for atmosphere adjustmentthat are composed of the same elements as the elements contained in thecomposite material powders are placed in the vicinity of the compositematerial powders. A temperature increase rate and a temperature decreaserate during firing are desirably 20 to 2,000° C./hour, and the time forholding a firing temperature is desirably 30 seconds to 10 hours.

A slight amount of sintering aids is desirably contained in thecomposite material powders. Sintering aids is desirably an oxidecontaining Li, and is more desirably at least one kind selected from thegroup consisting of Li₂O, Li₂O₂, LiNbO₃, Li₃NbO₄, LiTaO₃, Li₃TaO₄,LiSbO₃, Li₃SbO₄, Li(Nb, Ta, Sb)O₃ and Li₃(Nb, Ta, Sb)O₄. When thecomposite material powders contain sintering aids, sintered density of apiezoelectric/electrostrictive ceramic sintered body is improved.

A formed body of composite material powders is subjected to firing alonga generally used firing schedule. For example, firing is performed alonga one-step firing schedule (trapezoidal temperature profile) including(1) a first step of increasing a temperature from a room temperature toa first firing temperature of 900 to 1,300° C. (desirably, 900 to 1,100°C.) at a temperature increase rate of 20 to 2,000° C./hour (desirably,200° C./hour) and holding the first firing temperature for desirably 3hours, and after that, the temperature is immediately decreased to aroom temperature at a temperature decrease rate of 20 to 2,000° C./hour(desirably, 200° C./hour). Note that in this one-step firing schedule, apiezoelectric/electrostrictive ceramic sintered body is not densifiedsufficiently, whereby a relative density of thepiezoelectric/electrostrictive ceramic sintered body is less than 90% atmost.

Therefore, it is desirable that a formed body of composite materialpowders be subjected to firing along a multi-step firing schedulesimilar to that of a formed body of intermediate material powders ofadditional material phase. Alternatively, a formed body of compositematerial powders is subjected to firing along a multi-step firingschedule described below. For example, firing is performed along atwo-step firing schedule including: (1) a first step of increasing atemperature from a room temperature to 1,000 to 1,200° C. at atemperature increase rate of 300° C./hour or higher and holding thetemperature for 0.1 to 5 minutes; and (2) a second step of decreasingthe temperature to 700 to 1,000° C. at a temperature decrease rate of300 to 2,000° C./hour and holding the temperature for 0.5 to 30 hours,and after that, the temperature is decreased to a room temperature at atemperature decrease rate of 200° C./hour.

A formed body of composite material powders is more desirably subjectedto firing along a two-step firing schedule including: (1) a first stepof increasing a temperature from a room temperature to 1,000 to 1,100°C. at a temperature increase rate of 600° C./hour or higher and holdingthe temperature for 0.5 to 2 minutes; and (2) a second step ofdecreasing the temperature to 800 to 980° C. at a temperature decreaserate of 600° C./hour or higher and holding the temperature for 1 to 15hours, and after that, the temperature is decreased to a roomtemperature at a temperature decrease rate of 200° C./hour.

A formed body of composite material powders is desirably subjected tofiring under an oxygen atmosphere.

In this multi-step firing schedule, a piezoelectric/electrostrictiveceramic sintered body is densified sufficiently and a relative densityof a piezoelectric/electrostrictive ceramic sintered body reaches 90 to95% and, in some cases, 95 to 98%.

An electrode film is formed on a surface of thepiezoelectric/electrostrictive ceramic sintered body by screen printing,resistance heating deposition, sputtering or the like. The formed bodyof composite material powders and the electrode film may be integrallysubjected to firing. An electrode film may be formed inside thepiezoelectric/electrostrictive ceramic sintered body. Thepiezoelectric/electrostrictive ceramic sintered body may be processed bypolishing or cutting.

The piezoelectric/electrostrictive ceramic sintered body on which theelectrode film is formed is subjected to poling and aging. Aging isomitted in some cases.

In performing poling, the piezoelectric/electrostrictive ceramicsintered body on which the electrode film is formed is immersed ininsulating oil such as a silicon oil, whereby the electrode film isapplied with voltage. On this occasion, high-temperature poling isdesirably performed so as to heat the piezoelectric/electrostrictiveceramic sintered body to 50 to 150° C. When high-temperature poling isperformed, the piezoelectric/electrostrictive ceramic sintered body isapplied with a polarization field of 2 to 10 kV/mm. In a case ofperforming aging, the piezoelectric/electrostrictive ceramic sinteredbody is heated to 100 to 300° C. in the air atmosphere or oxygenatmosphere in a state in which the electrode film is open.

(Use)

The piezoelectric/electrostrictive ceramic sintered body according tothe first embodiment is preferably used in an actuator as described in asecond embodiment to a fifth embodiment. Note that use of thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment is not limited to an actuator. For example, thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment is also used in a piezoelectric/electrostrictiveelement such as a sensor.

2 Second Embodiment

The second embodiment relates to a single-layerpiezoelectric/electrostrictive actuator 1 using thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment.

(Outline of Piezoelectric/Electrostrictive Actuator 1)

FIG. 1 is a schematic view of the piezoelectric/electrostrictiveactuator 1 according to the second embodiment. FIG. 1 is across-sectional view of the piezoelectric/electrostrictive actuator 1.

As shown in FIG. 1, the piezoelectric/electrostrictive actuator 1 has astructure in which an electrode film 121, apiezoelectric/electrostrictive film 122 and an electrode film 123 arelaminated in this order on an upper surface of a substrate 11. Theelectrode films 121 and 123 on both principal surfaces of thepiezoelectric/electrostrictive film 122 are opposed to each other withthe piezoelectric/electrostrictive film 122 being sandwichedtherebetween. A laminate 12 in which the electrode film 121, thepiezoelectric/electrostrictive film 122 and the electrode film 123 arelaminated is united to the substrate 11.

“Uniting” refers to bonding the laminate 12 to the substrate 11 bysolid-phase reaction on an interface between the substrate 11 and thelaminate 12 without using an organic adhesive or inorganic adhesive. Alaminate may be bonded to a substrate by solid-phase reaction on aninterface between the substrate and a piezoelectric/electrostrictivefilm which is the lowermost layer of the laminate.

In the piezoelectric/electrostrictive actuator 1, upon application of avoltage to the electrode films 121 and 123, thepiezoelectric/electrostrictive film 122 expands and contracts in adirection perpendicular to an electric field in response to the appliedvoltage, and as a result, bending displacement is caused.

(Piezoelectric/Electrostrictive Film 122)

The piezoelectric/electrostrictive film 122 is apiezoelectric/electrostrictive ceramic sintered body.

A film thickness of the piezoelectric/electrostrictive film 122 isdesirably 0.5 to 50 μm, more desirably 0.8 to 40 μm, and particularlydesirably 1 to 30 μm. This is because the piezoelectric/electrostrictivefilm 122 tends to be insufficiently densified if the film thicknessthereof falls below this range. On the other hand, shrinkage stressduring sintering increases if the film thickness of thepiezoelectric/electrostrictive film 122 exceeds this range, and a platethickness of the substrate 11 needs to be increased, which makes itdifficult to miniaturize the piezoelectric/electrostrictive actuator 1.

(Electrode Films 121, 123)

A material for the electrode films 121 and 123 is metal such asplatinum, palladium, rhodium, gold and silver, or an alloy thereof.Among those, platinum or an alloy mainly composed of platinum isfavorable from the viewpoint of high heat resistance during firing.Alternatively, an alloy such as a silver-palladium alloy is favorablyused depending on firing temperature.

Film thicknesses of the electrode films 121 and 123 are desirably 15 μmor less, and more desirably 5 μm or less. This is because the electrodefilms 121 and 123 function as buffer layers if the film thicknesses ofthe electrode films 121 and 123 exceed this range, and thus bendingdisplacement tends to be small. Further, the film thicknesses of theelectrode films 121 and 123 are desirably 0.05 μm or more in order thatthe electrode films 121 and 123 appropriately perform their functions.

The electrode films 121 and 123 are desirably formed so as to cover aregion that is substantially conducive to bending displacement of thepiezoelectric/electrostrictive film 122. For example, the electrodefilms 121 and 123 are desirably formed so as cover a region of 80% ormore of both principal surfaces of the piezoelectric/electrostrictivefilm 122 which includes a center portion of thepiezoelectric/electrostrictive film 122.

(Substrate 11)

Although a material for the substrate 11 is ceramic, a type thereof isnot limited. However, from the viewpoints of heat resistance, chemicalstability and insulating property, it is desirably the ceramiccontaining at least one kind selected from the group consisting ofstabilized zirconium oxide, aluminum oxide, magnesium oxide, mullite,aluminum nitride, silicon nitride and glass. Among those, from theviewpoints of mechanical strength and tenacity, stabilized zirconiumoxide is more desirable. The “stabilized zirconium oxide” refers tozirconium oxide in which crystal phase transition is suppressed byaddition of a stabilizer, and includes partially-stabilized zirconiumoxide in addition to stabilized zirconium oxide.

Examples of the stabilized zirconium oxide include, for example,zirconium oxide containing, as a stabilizer, 1 to 30 mol % of calciumoxide, magnesium oxide, yttrium oxide, ytterbium oxide, cerium oxide oran oxide of rare earth metal. Among those, from the viewpoint ofparticularly high mechanical strength, zirconium oxide in which yttriumoxide is contained as a stabilizer. A content of yttrium oxide isdesirably 1.5 to 6 mol %, and more desirably 2 to 4 mol %. Further, inaddition to yttrium oxide, 0.1 to 5 mol % of aluminum oxide may bedesirably contained. A crystal phase of the stabilized zirconium oxidemay be a mixed crystal of a cubic crystal and a monoclinic crystal, amixed crystal of a tetragonal crystal and a monoclinic crystal, a mixedcrystal of a cubic crystal, a tetragonal crystal and a monocliniccrystal, or the like. The main crystal phase is desirably a mixedcrystal of a tetragonal crystal and a cubic crystal or a tetragonalcrystal from the viewpoints of mechanical strength, tenacity anddurability.

The plate thickness of the substrate 11 is uniform. The plate thicknessof the substrate 11 is desirably 1 to 1,000 μM, more desirably 1.5 to500 μm, and particularly desirably 2 to 200 μm. This is because themechanical strength of the piezoelectric/electrostrictive actuator 1tends to decrease if the plate thickness of the substrate 11 falls belowthis range. On the other hand, rigidity of the substrate 11 increases ifthe plate thickness of the substrate 11 exceeds this range, wherebybending displacement due to expansion and contraction of thepiezoelectric/electrostrictive film 122 when voltage is applied tends tobe small.

A shape of a surface (shape of a surface to which the laminate isunited) of the substrate 11 is not particularly limited, and may betriangular, quadrangular (rectangular or square), elliptic or circular,where corners may be rounded in the triangular shape and quadrangularshape. The shape may be a composite shape obtained by combining thosebasic shapes.

(Production of Piezoelectric/Electrostrictive Actuator 1)

In manufacturing the piezoelectric/electrostrictive actuator 1, theelectrode film 121 is formed on the substrate 11. The electrode film 121is formed using ion beam, sputtering, vacuum deposition, PVD (physicalvapor deposition), ion plating, CVD (chemical vapor deposition),plating, aerosol deposition, screen printing, spraying, dipping or othermethod. Among those, sputtering or screen printing is desirable from theviewpoint of bonding property between the substrate 11 and thepiezoelectric/electrostrictive film 122. The formed electrode film 122is united to the substrate 11 and the piezoelectric/electrostrictivefilm 122 through heat treatment. The temperature for heat treatmentdiffers in accordance with a material for the electrode film 121 and aforming method therefor, and is approximately 500 to 1,400° C.

Subsequently, the piezoelectric/electrostrictive film 122 is foamed onthe electrode film 121. The piezoelectric/electrostrictive film 122 isformed using ion beam, sputtering, vacuum deposition, PVD (physicalvapor deposition), ion plating, CVD (chemical vapor deposition),plating, sol-gel method, earosol deposition, screen printing, spraying,dipping or other method. Among those, considering that high accuracy isobtained in a planar shape and a film thickness and thatpiezoelectric/electrostrictive films can be successively formed, screenprinting is desirable.

Successively, the electrode film 123 is formed on thepiezoelectric/electrostrictive film 122. The electrode film 123 isformed in the same manner as the electrode film 121.

After the formation of the electrode film 123, the substrate 11 on whichthe laminate 12 is formed is integrally subjected to firing. Throughthis firing, sintering of the piezoelectric/electrostrictive film 122proceeds and the electrode films 121 and 123 are subjected to heattreatment as well.

Heat treatment of the electrode films 121 and 123 is preferablyperformed together with firing from the viewpoint of productivity, whichdoes not prevent the heat treatment from being performed every time theelectrode film 121 or 123 is formed. However, in the case where firingof the piezoelectric/electrostrictive film 122 is performed prior to theheat treatment of the electrode film 123, the electrode film 123 issubjected to heat treatment at a temperature lower than the firingtemperature of the piezoelectric/electrostrictive film 122.

After the firing, poling is performed on thepiezoelectric/electrostrictive actuator 1.

The piezoelectric/electrostrictive actuator 1 is also manufactured bythe green sheet laminating method that is commonly used in manufacturinglaminated-layer ceramic electronic parts. In the green sheet laminatingmethod, a binder, a plasticizer, a dispersing agent and a dispersingmedium are added to composite material powders, and ceramic, a binder, aplasticizer and a dispersing medium are mixed with a ball mill or thelike. The obtained slurry is formed into a sheet shape by doctor bladingor the like, whereby a formed body is obtained.

Subsequently, a film of electrode paste is printed on both principalsurfaces of the formed body by screen printing or the like. Theelectrode paste used in this case is obtained by adding a solvent,vehicle, glass frit and the like to the above-mentioned powders of metalor alloy.

Subsequently, the formed body in which the film of electrode paste isprinted on both principal surfaces thereof and the substrate arepress-bonded to each other.

Thereafter, the substrate on which the laminate is formed is integrallysubjected to firing and, after the firing, poling is performed.

3 Third Embodiment

The third embodiment relates to a multi-layerpiezoelectric/electrostrictive actuator 2 using thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment.

FIG. 2 is a schematic view of the piezoelectric/electrostrictiveactuator 2 according to the third embodiment. FIG. 2 is across-sectional view of the piezoelectric/electrostrictive actuator 2.

As shown in FIG. 2, the piezoelectric/electrostrictive actuator 2 has astructure in which an electrode film 221, apiezoelectric/electrostrictive film 222, an electrode film 223, apiezoelectric/electrostrictive film 224 and an electrode film 225 arelaminated in this order on an upper surface of a substrate 21. Theelectrode films 221 and 223 on both principal surfaces of thepiezoelectric/electrostrictive film 222 are opposed to each other withthe piezoelectric/electrostrictive film 222 being sandwichedtherebetween, and the electrode films 223 and 225 on both principalsurfaces of the piezoelectric/electrostrictive film 224 are opposed toeach other with the piezoelectric/electrostrictive film 224 beingsandwiched therebetween. A laminate 22 in which the electrode film 221,the piezoelectric/electrostrictive film 222, the electrode film 223, thepiezoelectric/electrostrictive film 224 and the electrode film 225 arelaminated is united to the substrate 21. Note that though FIG. 2 showsthe case of two layers of piezoelectric/electrostrictive films, three ormore layers of piezoelectric/electrostrictive films may be provided.

The substrate 21 of the piezoelectric/electrostrictive actuator 2 has asmaller plate thickness at a center portion 215 to which the laminate 22is bonded than at an edge 216. Accordingly, it is possible to increasebending displacement while keeping a mechanical strength of thesubstrate 21. The substrate 21 may be used in thepiezoelectric/electrostrictive actuator 1 according to the secondembodiment.

The piezoelectric/electrostrictive actuator 2 is also manufactured inthe same manner as the piezoelectric/electrostrictive actuator 1according to the second embodiment except that the number ofpiezoelectric/electrostrictive films and electrode films to be formedincrease.

4 Fourth Embodiment

The fourth embodiment relates to a multi-layerpiezoelectric/electrostrictive actuator 3 using thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment.

FIG. 3 is a schematic view of the piezoelectric/electrostrictiveactuator 3 according to the fourth embodiment. FIG. 3 is across-sectional view of the piezoelectric/electrostrictive actuator 3.

As shown in FIG. 3, the piezoelectric/electrostrictive actuator 3includes a substrate 31 in which a unit structure having a similarstructure to that of the substrate 21 according to the third embodimentis repeated. A laminate 32 having a similar structure to that of thelaminate 22 according to the third embodiment is united to each unitstructure of the substrate 31.

The piezoelectric/electrostrictive actuator 3 is also manufactured inthe same manner as the piezoelectric/electrostrictive actuator 1according to the second embodiment except that the number of laminatesand the number of piezoelectric/electrostrictive films and electrodefilms to be formed increase.

5 Fifth Embodiment

The fifth embodiment relates to a piezoelectric/electrostrictiveactuator 4 using the piezoelectric/electrostrictive ceramic sinteredbody according to the first embodiment.

FIG. 4 to FIG. 6 are schematic views of thepiezoelectric/electrostrictive actuator 4 according to the fifthembodiment. FIG. 4 is a perspective view of thepiezoelectric/electrostrictive actuator 4, FIG. 5 is a verticalcross-sectional view of the piezoelectric/electrostrictive actuator 4,and FIG. 6 is a lateral cross-sectional view of thepiezoelectric/electrostrictive actuator 4.

As shown in FIG. 4 to FIG. 6, the piezoelectric/electrostrictiveactuator 4 has a structure in which piezoelectric/electrostrictive films402 and internal electrode films 404 are alternately laminated in anaxis A direction, and external electrode films 416 and 418 are formed onend surfaces 412 and 414 of a laminate 410 in which thepiezoelectric/electrostrictive films 402 and the internal electrodefilms 404 are laminated.

As shown in an exploded perspective view of FIG. 7 which shows a statein which part of the piezoelectric/electrostrictive actuator 4 isdisassembled in the axis A direction, the internal electrode films 404are classified into first internal electrode films 406 which reach theend surface 412 but do not reach the end surface 414 and second internalelectrode films 408 which reach the end surface 414 but do not reach theend surface 412. The first internal electrode films 406 and the secondinternal electrode films 408 are alternately provided. The firstinternal electrode films 406 are in contact with the external electrodefilm 416 on the end surface 412, and are electrically connected to theexternal electrode film 416. The second internal electrode films 408 arein contact with the external electrode film 418 on the end surface 414,and are electrically connected to the external electrode film 418.Accordingly, when the external electrode film 416 is connected to a plusside of a driving signal source and the external electrode film 418 isconnected to a minus side of the driving signal source, a driving signalis applied to the first internal electrode film 406 and the secondinternal electrode film 408 which are opposed to each other with thepiezoelectric/electrostrictive film 402 sandwiched therebetween, wherebyan electric field is applied in the thickness direction of thepiezoelectric/electrostrictive film 402. As a result, thepiezoelectric/electrostrictive films 402 expand and contract in thethickness direction, whereby the laminate 410 deforms into the shapeindicated by a dotted line of FIG. 4 as a whole.

In contrast to the piezoelectric/electrostrictive actuators 1 to 3described above, the piezoelectric/electrostrictive actuator 4 does notinclude a substrate to which the laminate 410 is united. In addition,the piezoelectric/electrostrictive actuator 4 is also referred to as an“offset type piezoelectric/electrostrictive actuator” because the firstinternal electrode films 406 and the second internal electrode films 408having different patterns are alternately provided therein.

The piezoelectric/electrostrictive film 402 is thepiezoelectric/electrostrictive ceramic sintered body according to thefirst embodiment. A film thickness of the piezoelectric/electrostrictivefilm 402 is preferably 5 to 500 μm. This is because it is difficult tomanufacture a green sheet described below if the film thickness fallsbelow this range. On the other hand, it is difficult to apply asufficient electric field to the piezoelectric/electrostrictive film 402if the film thickness exceeds this range.

A material for the internal electrode film 404 and the externalelectrode films 416 and 418 is metal such as platinum, palladium,rhodium, gold and silver, or an alloy thereof. Among those, the materialfor the internal electrode film 404 is preferably platinum or an alloymainly composed of platinum because heat resistance during firing ishigh and co-sintering with the piezoelectric/electrostrictive film 402is performed easily. However, an alloy such as a silver-palladium alloyis preferably used depending on the firing temperature.

A film thickness of the internal electrode film 402 is desirably 10 μmor less. This is because the internal electrode film 402 functions as abuffer layer if the film thickness exceeds this range, wherebydisplacement tends to decrease. In order to cause the internal electrodefilm 402 to appropriately perform its function, the film thickness isdesirably 0.1 μm or more.

Note that though FIG. 4 to FIG. 6 show the case of ten layers of thepiezoelectric/electrostrictive films 402, nine or less, or eleven ormore layers of the piezoelectric/electrostrictive films 402 may beprovided.

In manufacturing the piezoelectric/electrostrictive actuator 4, abinder, a plasticizer, a dispersing agent and a dispersing medium areadded to composite material powders, and those are mixed with a ballmill or the like. The obtained slurry is formed into a sheet shape bydoctor blading or the like, whereby a green sheet is obtained.

Subsequently, the green sheet is subjected to punching process using apunch or die, whereby a hole or the like for alignment is formed in thegreen sheet.

Subsequently, an electrode paste is applied onto the surface of thegreen sheet by screen printing or the like, whereby the green sheet onwhich a pattern of the electrode paste is formed is obtained. Thepattern of the electrode paste is classified into two types of a firstpattern of the electrode paste which becomes the first internalelectrode film 406 after firing and a second pattern of the electrodepaste which becomes the second internal electrode film 408 after firing.Needless to say, only one type of pattern of electrode paste may beemployed so that directions of the green sheets are rotated by 180degrees every other sheet, to thereby obtain the internal electrodefilms 406 and 408 after firing.

Then, the green sheets on which the first pattern of the electrode pasteis formed and the green sheets on which the second pattern of theelectrode paste is formed are alternately laminated on each other, andthe green sheet onto which the electrode paste is not applied islaminated on the uppermost part. After that, the laminated green sheetsare pressurized and press-bonded in the thickness direction. On thisoccasion, positions of holes for alignment, which are formed in thegreen sheets, are caused to coincide with each other. Further, inpress-bonding the laminated green sheets, the green sheets are desirablypress-bonded while being heated by heating a die used for press-bondingin advance.

The press-bonded body of green sheets thus obtained is subjected tofiring, and the obtained sintered body is processed with a dicing saw orthe like, whereby the laminate 410 is obtained. Then, the externalelectrode films 416 and 418 are formed on the end surfaces 412 and 414of the laminate 410, respectively, by firing, vapor deposition,sputtering and the like, and poling is performed, whereby thepiezoelectric/electrostrictive actuator 4 is obtained.

EXAMPLE Experiment 1 Production of Material Powders of Matrix Phase

Raw materials of lithium carbonate (Li₂CO₃), sodium bitartratemonohydrate (C₄HSO₆Na.H₂O), potassium bitartrate (C₄H₅O₆K), niobiumoxide (Nb₂O₅), tantalum oxide (Ta₂O₅), antimony oxide (Sb₂O₃), bariumcarbonate (BaCO₃), manganese dioxide (MnO₂) and the like were weighed soas to have the composition of a matrix phase in Table 1, and then weremixed together with a ball mill.

The obtained mixed material was subjected to calcination for 5 hours at800° C. and ground with a ball mill two times, to thereby obtainmaterial powders of a matrix phase with a median particle diameter of0.5 μm and a maximum particle diameter of 1 μm.

(Production of Material Powders of Additional Material Phase)

Raw materials of lithium carbonate, sodium bitartrate monohydrate,potassium bitartrate, niobium oxide, tantalum oxide, antimony oxide,barium carbonate, manganese dioxide and the like were weighed so as tohave the composition of an additional material phase in Table 1, andthen were mixed together with a ball mill.

The obtained mixed material was subjected to calcination for 5 hours at800° C. and ground with a ball mill two times, to thereby obtainintermediate material powders of an additional material phase.

The obtained intermediate material powders of additional material phasewere subjected to pressing to be formed in a disk shape having adiameter of 18 mm and a plate thickness of 5 mm at a pressure of 2×10⁸Pa. Then, the obtained formed body was subjected to firing at 900° C. orhigher.

The piezoelectric/electrostrictive ceramic sintered body formed of theobtained additional material phase alone was ground and classified, tothereby obtain material powders of additional material phase with amedian particle diameter of 0.6 to several μm and a maximum particlediameter of 10 μm.

(Production of Composite Material Powders)

Material powders of matrix phase and material powders of additionalmaterial phase were weighed and mixed together such that the content ofadditional material phase in a piezoelectric/electrostrictive ceramicsintered body is the content of Table 2.

(Production of Piezoelectric/Electrostrictive Element for Evaluation)

The produced composite material powders, material powders of matrixphase and material powders of additional material phase were subjectedto pressing to be formed in a disk shape having a diameter of 18 mm anda plate thickness of 5 mm at a pressure of 2×10⁸ Pa. Then, the formedbody was housed in an alumina container and then subjected to firing, tothereby obtain a piezoelectric/electrostrictive ceramic sintered body.

A formed body of composite material powders was subjected to firingalong the above-mentioned two-step firing schedule, and a formed body ofmaterial powders of matrix phase and a formed body of material powdersof additional material phase were subjected to firing along theabove-mentioned one-step firing schedule. The relative densities of theobtained sintered bodies were all 90 to 95%.

Subsequently, the sintered body was processed into a rectangular shapehaving a long side of 12 mm, a short side of 3 mm, and a thickness of 1mm, and then was subjected to heat treatment at 600 to 900° C. Afterthat, gold electrodes were formed on both principal surfaces of therectangular sample by sputtering.

(Residual Strain Ratio)

In the piezoelectric/electrostrictive element processed from apiezoelectric/electrostrictive ceramic sintered body of a matrix phasealone or an additional material phase alone, a residual strain in a longside direction, which was obtained by applying a voltage of 4 kV/mm tothe electrodes of both principal surfaces of thepiezoelectric/electrostrictive element that has not been subjected topoling and then stopping application of voltage, was measured with astrain gauge attached to the electrode with an adhesive, and theresidual strain was divided by the length of the long side of thepiezoelectric/electrostrictive element, to thereby calculate a residualstrain ratio. The results thereof are shown in Table 1.

(Electric Field Induced Strain)

In the piezoelectric/electrostrictive element processed from apiezoelectric/electrostrictive ceramic sintered body of a matrix phasealone and a piezoelectric/electrostrictive ceramic sintered body thathas been made into a composite, the reversible strain in a long sidedirection when a voltage of 4 kV/mm was applied to the electrodes ofboth principal surfaces of the piezoelectric/electrostrictive elementthat has been subjected to poling was measured with a strain gaugeattached to the electrode with an adhesive, and the reversible strainwas divided by the length of the long side of thepiezoelectric/electrostrictive element, to thereby calculate an electricfield induced strain S₄₀₀₀ (ppm). The results thereof are shown in Table2.

(Effects of Compositization)

As in Experiment 1, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase and a difference between a residual strainratio of matrix phase alone and a residual strain ratio of additionalmaterial phase alone was 190 ppm, more excellent electric field inducedstrain S₄₀₀₀ compared with a matrix phase alone was obtained when thecontent of additional material phase was 1 to 45% by volume. Further,much more excellent electric field induced strain S₄₀₀₀ was obtainedwhen the content was 2 to 35% by volume, and particularly excellentelectric field induced strain S₄₀₀₀ was obtained when the content was 4to 25% by volume.

TABLE 1 Experiment 1 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.05 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Element that is not common to both n/a Residual strainratio of additional material phase alone 960 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 190ppm

TABLE 2 Experiment 1 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 685 715 725 745 760730 715 640 610 (ppm)

Experiment 2

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 3 and Table 4. As to theadditional material phase, a Ba amount was increased compared withExperiment 1.

As in Experiment 2, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase and a difference between a residual strainratio of matrix phase alone and a residual strain ratio of additionalmaterial phase alone was 240 ppm, more excellent electric field inducedstrain S₄₀₀₀ compared with a matrix phase alone was obtained when thecontent of additional material phase was 1 to 45% by volume. Further,the effect of improving an electric field induced strain S₄₀₀₀ due tocompositization was enhanced as a result of a larger difference betweena residual strain ratio of a matrix phase alone and a residual strainratio of an additional material phase alone.

TABLE 3 Experiment 2 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Element that is not common to both n/a Residual strainratio of additional material phase alone 1,010 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 240ppm

TABLE 4 Experiment 2 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 705 735 760 785 780755 740 650 610 (ppm)

Experiment 3

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 5 and Table 6. As to theadditional material phase, a Sb amount was decreased and a Ba amount wasincreased compared with Experiment 1.

As in Experiment 3, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase and a difference between a residual strainratio of a matrix phase alone and a residual strain ratio of anadditional material phase alone was 40 ppm, more excellent electricfield induced strain S₄₀₀₀ compared with a matrix phase alone wasobtained when the content of additional material phase was 1 to 45% byvolume. Note that the effect of improving the electric field inducedstrain S₄₀₀₀ due to compositization was reduced as a result of a smallerdifference between a residual strain ratio of a matrix phase alone and aresidual strain ratio of an additional material phase alone.

TABLE 5 Experiment 3 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.977)Ta_(0.022)Sb_(0.001))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Element that is not common to both n/a Residual strainratio of additional material phase alone 810 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 40ppm

TABLE 6 Experiment 3 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 650 650 655 660 650650 645 625 610 (ppm)

Experiment 4

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 7 and Table 8. As to theadditional material phase, an A/B ratio was increased and a Ba amountwas increased compared with Experiment 1.

As in Experiment 4, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase and a difference between a residual strainratio of a matrix phase alone and a residual strain ratio of anadditional material phase alone was 300 ppm, more excellent electricfield induced strain S₄₀₀₀ compared with a matrix phase alone wasobtained when the content of additional material phase was 1 to 45% byvolume. Further, the effect of improving the electric field inducedstrain S₄₀₀₀ due to compositization was increased as a result of alarger difference between a residual strain ratio of a matrix phasealone and a residual strain ratio of an additional material phase alone.

TABLE 7 Experiment 4 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.10)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Element that is not common to both n/a Residual strainratio of additional material phase alone 1,070 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 300ppm

TABLE 8 Experiment 4 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 720 760 790 810 810790 760 650 610 (ppm)

Experiment 5

An experiment was performed in a similar procedure to that of Experiment1 except for that the compositions of additional material phase andmatrix phase were changed. The results thereof are shown in Table 9 andTable 10. As to the additional material phase, a Ba amount was increasedcompared with Experiment 1. As to the matrix phase, a Ba amount wasincreased compared with Experiment 1, and in place of adding a Mncompound, part of B-site constituent element was substituted by Mn.

As in Experiment 5, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase, and a difference between a residual strainratio of a matrix phase alone and a residual strain ratio of anadditional material phase alone was 220 ppm, more excellent electricfield induced strain S₄₀₀₀ compared with a matrix phase alone wasobtained when the content of additional material phase was 1 to 45% byvolume.

TABLE 9 Experiment 5 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.1 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.874)Ta_(0.081)Sb_(0.040)Mn_(0.005))O₃:100 parts by mole Ba oxide: 0.5 parts by mole Constituent elements ofadditional material phase Li, K, Na, Nb, Ta, Sb, Ba, Mn, O Constituentelements of matrix phase Li, K, Na, Nb, Ta, Sb, Ba, Mn, O Element thatis not common to both n/a Residual strain ratio of additional materialphase alone 1,010 ppm Residual strain ratio of matrix phase alone 790ppm Difference in residual strain ratio: 220 ppm

TABLE 10 Experiment 5 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 675 705 725 750 750725 710 635 610 (ppm)

Experiment 6

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 11 and Table 12. Theadditional material phase does not contain Ta differently fromExperiment 1.

As in Experiment 6, even if there was one type of element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase, in a case where a difference between aresidual strain ratio of a matrix phase alone and a residual strainratio of an additional material phase alone was large, such as 330 ppm,more excellent electric field induced strain S₄₀₀₀ compared with amatrix phase alone was obtained when the content of additional materialphase was 1 to 45% by volume.

TABLE 11 Experiment 6 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.960)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb, Ta,Sb, Ba, Mn, O Element that is not common to both Ta Residual strainratio of additional material phase alone 1,100 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 330ppm

TABLE 12 Experiment 6 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 730 780 810 830 830810 770 655 610 (ppm)

Experiment 7

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of matrix phase was changed. Theresults thereof are shown in Table 13 and Table 14. The matrix phasedoes not contain Ba differently from Experiment 1.

As in Experiment 7, even if there was one type of element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase, in a case where a difference between aresidual strain ratio of a matrix phase alone and a residual strainratio of an additional material phase alone was large, such as 400 ppm,more excellent electric field induced strain S₄₀₀₀ compared with amatrix phase alone was obtained when the content of additional materialphase was 1 to 45% by volume.

TABLE 13 Experiment 7 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.05 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Mn oxide: 0.02 parts by mole Constituent elements ofadditional material phase Li, K, Na, Nb, Ta, Sb, Ba, Mn, O Constituentelements of matrix phase Li, K, Na, Nb, Ta, Sb, Mn, O Element that isnot common to both Ba Residual strain ratio of additional material phasealone 960 ppm Residual strain ratio of matrix phase alone 560 ppmDifference in residual strain ratio: 400 ppm

TABLE 14 Experiment 7 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 670 675 685 685 675670 665 640 610 (ppm)

Experiment 8

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of matrix phase was changed. Theresults thereof are shown in Table 15 and Table 16. The matrix phasecontains Bi and does not contain Sb and Ba differently from Experiment1.

As in Experiment 8, in a case where there were three types of elementsthat were not common to constituent elements of matrix phase andconstituent elements of additional material phase, the effect ofimproving the electric field induced strain S₄₀₀₀ due to compositizationwas not confirmed even if a difference between a residual strain ratioof a matrix phase alone and a residual strain ratio of an additionalmaterial phase alone was large, such as 340 ppm.

TABLE 15 Experiment 8 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.05 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.06)(K_(0.45)Na_(0.55))_(0.94)}_(1.01)(Nb_(0.918)Ta_(0.082))O₃:100 parts by mole Bi oxide: 0.05 parts by mole Mn oxide: 0.05 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Bi, Mn, O Elements that are not common to both Sb, Ba, Bi Residualstrain ratio of additional material phase alone 960 ppm Residual strainratio of matrix phase alone 620 ppm Difference in residual strain ratio:340 ppm

TABLE 16 Experiment 8 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 720 710 705 705 705 700700 690 680 670 (ppm)

Experiment 9

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of matrix phase was changed. Theresults thereof are shown in Table 17 and Table 18. The matrix phasecontains Bi and does not contain Ba differently from Experiment 1.

As in Experiment 9, in a case where there were two types of elementsthat were not common to constituent elements of matrix phase andconstituent elements of additional material phase, the effect ofimproving the electric field induced strain S₄₀₀₀ due to compositizationwas extremely small even if a difference between a residual strain ratioof a matrix phase alone and a residual strain ratio of an additionalmaterial phase alone was large, such as 430 ppm.

TABLE 17 Experiment 9 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.05 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.06)(K_(0.45)Na_(0.55))_(0.94)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Bi oxide: 0.05 parts by mole Mn oxide: 0.05 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Bi, Mn, O Elements that are not common to both Ba, Bi Residualstrain ratio of additional material phase alone 960 ppm Residual strainratio of matrix phase alone 530 ppm Difference in residual strain ratio:430 ppm

TABLE 18 Experiment 9 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 680 690 695 700 715 700700 695 690 680 (ppm)

Experiment 10

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 19 and Table 20. As tothe additional material phase, an A/B ratio was increased, a Nb amountwas increased, and a Sb amount was decreased compared with Experiment 1.The additional material phase does not contain Ta differently fromExperiment 1.

As in Experiment 10, even if there was one type of element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase, in a case where a difference between aresidual strain ratio of a matrix phase alone and a residual strainratio of an additional material phase alone was large, such as 410 ppm,more excellent electric field induced strain S₄₀₀₀ compared with thematrix phase alone was obtained and an improvement of the electric fieldinduced strain S₄₀₀₀ of approximately 45% was observed at most when thecontent of additional material phase was 1 to 45% by volume.

TABLE 19 Experiment 10 Composition of additional material phase{Li_(0.07)(K_(0.45)Na_(0.55))_(0.93)}_(1.10)(Nb_(0.980)Sb_(0.020))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb, Ta,Sb, Ba, Mn, O Element that is not common to both Ta Residual strainratio of additional material phase alone 1,180 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 410ppm

TABLE 20 Experiment 10 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 615 750 810 840 890 890845 790 735 615 (ppm)

Experiment 11

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 21 and Table 22. As tothe additional material phase, a Li amount was decreased compared withExperiment 1.

As in Experiment 11, in a case where there was no element that was notcommon to constituent elements of matrix phase and constituent elementsof additional material phase and a difference between a residual strainratio of matrix phase alone and a residual strain ratio of additionalmaterial phase alone was 260 ppm, more excellent electric field inducedstrain S₄₀₀₀ compared with the matrix phase alone was obtained when thecontent of additional material phase was 1 to 45% by volume.

TABLE 21 Experiment 11 Composition of additional material phase{Li_(0.04)(K_(0.45)Na_(0.55))_(0.96)}_(1.01)(Nb_(0.938)Ta_(0.022)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.05 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb,Ta, Sb, Ba, Mn, O Element that is not common to both n/a Residual strainratio of additional material phase alone 1,030 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 260ppm

TABLE 22 Experiment 11 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 615 695 740 770 790 790770 740 635 615 (ppm)

Experiment 12

An experiment was performed in a similar procedure to that of Experiment1 except for that the composition of additional material phase waschanged. The results thereof are shown in Table 23 and Table 24. As tothe additional material phase, an A/B ratio was increased, a Li amountwas decreased, Nb was increased, and a Sb amount was decreased comparedwith Experiment 1. The additional material phase does not contain Ta,differently from Experiment 1.

As in Experiment 12, even if there was one element that was not commonto constituent elements of matrix phase and constituent elements ofadditional material phase, in a case where a difference between aresidual strain ratio of matrix phase alone and a residual strain ratioof additional material phase alone was large, such as 560 ppm, moreexcellent electric field induced strain S₄₀₀₀ compared with the matrixphase alone was obtained and an improvement of the electric fieldinduced strain S₄₀₀₀ of approximately 50% at most was observed when thecontent of additional material phase was 1 to 45% by volume.

TABLE 23 Experiment 12 Composition of additional material phase{Li_(0.04)(K_(0.45)Na_(0.55))_(0.96)}_(1.10)(Nb_(0.980)Sb_(0.020))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Composition of matrix phase{Li_(0.07)(K_(0.36)Na_(0.64))_(0.93)}_(1.01)(Nb_(0.878)Ta_(0.082)Sb_(0.040))O₃:100 parts by mole Ba oxide: 0.10 parts by mole Mn oxide: 0.02 parts bymole Constituent elements of additional material phase Li, K, Na, Nb,Sb, Ba, Mn, O Constituent elements of matrix phase Li, K, Na, Nb, Ta,Sb, Ba, Mn, O Element that is not common to both Ta Residual strainratio of additional material phase alone 1,330 ppm Residual strain ratioof matrix phase alone 770 ppm Difference in residual strain ratio: 560ppm

TABLE 24 Experiment 12 Content of 0 1 2 4 10 20 25 35 45 50 additionalmaterial phase (% by volume) Strain ratio S₄₀₀₀ 610 740 840 890 945 945890 790 740 610 (ppm)

The foregoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

EXPLANATION OF REFERENCED NUMERALS

-   -   1, 2, 3, 4 piezoelectric/electrostrictive actuator    -   122, 222, 224, 402 piezoelectric/electrostrictive film    -   121, 123, 221, 223, 225 electrode film    -   404 internal electrode film

The invention claimed is:
 1. A piezoelectric/electrostrictive ceramicsintered body having a microstructure in which a matrix phase and anadditional material phase having different compositions coexist and theadditional material phase is dispersed in the matrix phase, wherein: aresidual strain ratio of the additional material phase alone is largerthan a residual strain ratio of the matrix phase alone; a composition ofthe matrix phase and a composition of the additional material phase areselected from a composition range of a composite in which at least oneof a Mn compound, containing Mn atoms of 0.001 parts by mole or more and3 parts by mole or less, and a Ba compound, containing Ba atoms of 0.01parts by mole or more and 1 part by mole or less, are contained in acompound of 100 parts by mole represented by a general formula{Li_(y)(Na_(1-x)K_(x))_(1-y)}_(a)(Nb_(1-z-w)Ta_(z)Sb_(w))O₃, where a, x,y, z and w satisfy 0.9≦a≦1.2, 0.2≦x≦0.8, 0.0≦y≦0.2, 0≦z≦0.5 and 0≦w≦0.1,respectively; zero or one kind of element is not common to constituentelements of the matrix phase and constituent elements of the additionalmaterial phase in comparison therebetween; wherein the composition ofthe additional material phase alone is selected so that the residualstrain ratio in a long side direction of a rectangular plate polarizedin a thickness direction of the additional material phase is 800 ppm ormore; and wherein part or all of said at least one Mn compound and Bacompound forms a solid solution with said compound.
 2. Thepiezoelectric/electrostrictive ceramic sintered body according to claim1, which contains the additional material phase of 1% by volume or moreand 45% by volume or less.
 3. The piezoelectric/electrostrictive ceramicsintered body according to claim 1, wherein z of the additional materialphase is smaller than z of the matrix phase.
 4. Thepiezoelectric/electrostrictive ceramic sintered body according to claim1, wherein y of the additional material phase is smaller than y of thematrix phase.
 5. The piezoelectric/electrostrictive ceramic sinteredbody according to claim 1, wherein a of the additional material phase islarger than a of the matrix phase.
 6. The piezoelectric/electrostrictiveceramic sintered body according to claim 1, wherein w of the additionalmaterial phase is smaller than w of the matrix phase.
 7. Thepiezoelectric/electrostrictive ceramic sintered body according to claim1, wherein x of the additional material phase is larger than x of thematrix phase.
 8. The piezoelectric/electrostrictive ceramic sinteredbody according to claim 2, wherein z of the additional material phase issmaller than z of the matrix phase.
 9. Thepiezoelectric/electrostrictive ceramic sintered body according to claim2, wherein y of the additional material phase is smaller than y of thematrix phase.
 10. The piezoelectric/electrostrictive ceramic sinteredbody according to claim 3, wherein y of the additional material phase issmaller than y of the matrix phase.
 11. Thepiezoelectric/electrostrictive ceramic sintered body according to claim2, wherein a of the additional material phase is larger than a of thematrix phase.
 12. The piezoelectric/electrostrictive ceramic sinteredbody according to claim 3, wherein a of the additional material phase islarger than a of the matrix phase.
 13. Thepiezoelectric/electrostrictive ceramic sintered body according to claim4, wherein a of the additional material phase is larger than a of thematrix phase.
 14. The piezoelectric/electrostrictive ceramic sinteredbody according to any one of claim 2, wherein w of the additionalmaterial phase is smaller than w of the matrix phase.